1. Field
The following description relates to a device for predicting underground behavior by using an acoustic emission (AE) sensor that monitors an underground dynamic state or behavior by inserting a waveguide rod with a reliable and superior acoustic emission sensor into an underground, and predicts a possibility of collapse, and a producing method thereof.
2. Description of the Related Art
Regional torrential rains, super typhoon, flood, etc. due to climatic change cause frequent landslides, losses of a slope and collapses, thereby requiring development of technology for preventing geological disasters.
It is required to follow a process of extracting a behavior of bedrock or a ground as a proper signal in order to predict or estimate stability of a disintegrable target land and then analyzing the behavior. A sensor is needed to obtain a signal according to the behavior and most precisely send an environment inside the bedrock or the ground. General technologies or devices used for predicting collapse of the ground structure include a displacement measuring method using an underground displacement gauge, underground clinometers, or Global Positioning Systems (GPS), a measuring method of fluctuations of ground-water level using a piezometer, and a stress measuring method using a load gauge.
However, since a variance is very small until the collapse of the ground or the bedrock and it is not easy to find a feature in occurrence tendency of stress or variance, it is difficult to notice a sign of collapse by the displacement or stress measuring methods. An acoustic emission sensor is prepared to solve the difficulty in predicting the sign of collapse. The acoustic emission sensor uses a microscopic breaking sound generated inside an object at an early stage that the object is broken as a signal. The acoustic emission (AE) is an elastic wave generated when deformation energy accumulated in materials is suddenly emitted. There is a general tendency that generation of the acoustic emission remarkably increases before a full-scale collapse.
JP Patent Laid-Open No. 1996-062337, which is related to a device for predicting a behavior in a ground or bedrock by using AE, discloses a method for inserting a waveguide filling an acoustic emission generating layer into a borehole. However, the waveguide is spaced apart from the inner wall of the borehole and there is a disadvantage that the change of the ground stress is not sufficiently transferred to the waveguide.
KR Patent Publication No. 2009-0117402 discloses a method of inserting a metal rod for transferring AE into a borehole and fixing the metal rod using cement. However, in a grouting process, there is a possibility that non-homogeneity of materials increases due to change of proportions according to cement sieving, i.e., depth. Accordingly, acoustic emission is differently generated to cause deterioration of reliability in measurement values.